The present invention relates to a flow passage coupling unit for connection and disconnection of pipings e.g. on a tooling die exchanger device of a press or a forming machine.
There has been known such a prior art flow passage coupling unit shown in FIG. 8 (also disclosed in Japanese Utility Model Pre-examined Publication No. 167888/1985).
The prior art flow passage coupling unit is arranged in which a first coupling component 53 cosisting of a main body 51 and a slide valve 52 is mounted to an instrument 50 which is supportedly provided for forward and backward movement (leftward and rightward of FIG. 8) and for connection with a piping at the other end, and another instrument 55 which acts as a second coupling component 55 having a coupling surface 65 thereof where a flow path 54' is made open, is disposed opposite to the first coupling component 53 as represented by the chain line of FIG. 8.
The main body 51 of the first coupling component 53 which is fixedly supported by the instrument 60, incorporates a large diameter bore 56 communicated with a flow path 54 in the instrument 50, a small diameter bore 57 into which the slide valve 52 is slidably fitted, and a valve seat 58 provided in the form of a tapered surface (of conical configuration) between the large and small diameter bores 56 and 57.
The slide valve 52 comprises a cylindrical body 70 and a valve head 63 fixedly mounted to a rear end waIl 73 of the cylindrical body 70. The slide valve 62 is kept urged by a spring 64 installed in the large diameter bore 56 so that its valve head 63 can be seated on the valve seat 58. The valve head 63 includes a seal member 62 arranged in contact with the valve seat 58 and is joined by a bolt 74 to the rear end wall 73 of the cylindrical body 70. The cylindrical body 70 incorporates a rear end surface 72 and a front end surface 71 which constitute the rear end wall 73 and has a through hole 60 provided therein adjacent to the rear end wall 73 for communicating with the large diameter bore 56 when the valve head 63 is unseated. There is a fluid passage bore 59 communicated with the through hole 60 and at the other end, arranged open in an end surface 75 of the cylindrical body 70 to define an opening end 78. The end surface 75 is provided with a resilient seal member 61 of rectangular shape in cross section having a uniform thickness and bonded around the opening end 78 to the area thereof which is defined by an inner wall 76 of the fluid passage bore 59 and an outer wall 77 of the cylindrical body 70.
According to the above arrangement in the prior art flow passage coupling unit, compressed air supplied from the flow passage 54 to the large diameter bore 56 remains trapped within the large diameter bore 56 as the valve head 63 and the valve seat 58 abut each other for closing. Then, the instrument 50 is advanced to cause the resilient seal member 61 of the slide valve 52 to press against the coupling surface 65 of the instrument 55. When a greater force of pressure is exerted on the instrument 50 than the sum of an air pressure on the slide valve 52 and a yielding force of the spring 64, the slide valve 52 moves relatively to the backward. The seal member 62 on the valve head 63 then departs from the valve seat 58 and the through hole 60 in the cylindrical body 70 becomes communicated with the large diameter bore 56. As the through hole 60 is unclosed to the large diameter bore 56, the pressure by the compressed air exerted on the valve head 63 is released while the yielding force of the spring 64 remains. As the instrument 50 advances further towards the instrument 55, the communication between the through hole 60 and the large diameter bore 56 is enhanced corresponding to the distance of movement. When the through hole 60 is completely open to the large diameter bore 56, the flow paths 54 and 54' will be communicated with each other.
The cylindrical body 70 of the slide valve 52 in the flow passage coupling unit can slide through the small diameter bore 57 in the main body 51 while the valve head 63 of the slide valve 52 has no contact with the inner side of the large diameter bore 56 of the main body 51 after departing from the valve seat 58. Accordingly, the stable movement of the slide valve 52 during flow passage connection depends on the distance L of axial sliding of the cylindrical body 70 through the small diameter bore 51. The sliding distance L is preliminarily determined so that its ratio to the diameter D of the cylindrical body 70 is more than a specified rate. More particularly, it is necessary for assuring the stable movement of the slide valve 52 to lengthen the sliding distance L in relation to the diameter D in order to keep the ratio greater than the specified rate if the diameter D of the cylindrical body 70 is somewhat large. Consequently, the relative sliding distance L to the diameter D of the cylindrical body 70 has to be increased to ensure the area of satisfactory fluid passing for the purpose of reducing resistance to flow. Thus, the disadvantage is that the axial length of the small diameter bore 57 increases and the entire coupling unit becomes great in axial length.